isnt itunes u only for podcasts? and i cant seem to find any textbooks in ibooks
At the moment the dedicated Textbook section is only on the US store. The only ibooks of this type are the Dorling Kindersley and the biology book sampler (2 chapters) by E.O. Wilson. You can search for these and download them.
I'm afraid you'll probably have to wait a few months for serious textbooks for uni/college to start filtering through.
iTunes U was just podcasts, but some had pdf docs attached. What the iTunesU app does is give the lecturers the opportunity to pull all the video/audio/worksheets supporting iBooks if they exist, supporting apps, pdf's and website url's into a cohesive learning plan.
The iPad is awesome for reviewing PDF's and if you are an english major with a lot of books to review, it's great for iBooks and/or kindle.
Other textbooks, you'll just have to wait a bit longer.